1. Technical Field of the Invention
The present invention relates to networked communications systems, and in particular, to a system and method operating within a communications network providing the ability to restart nodal entity timers along extended message pathways so as to preclude unnecessary timeout errors.
2. Description of Related Art
Within a communications network messages are passed between terminal points, which may also be characterized as nodal entities. The usual order of communication involves a message sent from a first node to a second node, and a response or reply, prompted by sending the initial message, sent from the second node to the first node. For various reasons, such as the presence of excessive electronic noise or a physical fault in the network, the response may never reach the first node.
Timers have been built into network nodes to ensure that the failure to receive a response does not result in network inactivity for an indefinite period. That is, when a message is sent from one node to another, a timer within the sending node is typically started and allowed to run for a preselected period of time. If no response is received before the timeout period of the timer (i.e., timer count down to a value of zero), then the sending node is alerted to this fact and appropriate recovery measures can be taken. For example, a second message may be sent into the network to determine the reason for the fault condition, or the same message may be re-sent along a different pathway. In any case, it is the timer within the sending node that determines the amount of time for which response to any particular message is allowed.
As a matter of efficiency, nodal response timers are typically set to a fixed timeout value. For example, within a telecommunications network comprising a plurality of Mobile Switching Centers (MSCs), each MSC typically comprises an operation transaction timer, or response timer, with a static default timeout value limit of about 10 seconds. The American National Standards Institute (ANSI) 41-D Standard provides a summary description of response timers and their timeout values, as used during Mobile Application Part (MAP) operations. The timeout values are specified as default values, and are supposed to be optimized for each specific operating environment. These default values are successfully used when a minimal number of nodes are involved in any particular communications scenario. However, during more complex transactions, e.g., hand-off with Tandem, Short Message Service (SMS), Code Division Multiple Access (CDMA), authentication, international roaming, and various Wireless Intelligent Network (WIN) services, where three or more nodes are involved in the same transaction, the default values may not be sufficient to ensure receipt of a response before a timeout error is generated within the original sending node. That is, the original sending node may use a default timeout value which is too short to allow processing of the message by a second node, which in turn must communicate with a third node (and so on) in order to provide a response to the message sent by the first node.
Another example of this problem may be seen in the operation of inter-exchange handoff operations. Inter-exchange handoffs involve passing off mobile telephone call connections from one MSC to another. Within a handoff operation, four types of MSC exchanges are typically present: an anchor exchange, the MSC from which the call is originated; a serving exchange, the MSC presently serving the call; a Tandem MSC, which previously handed off the call to the Serving MSC; and a target exchange, an MSC to which the call is to be handed off. A handoff from the serving exchange to an exchange involved in the call path is known as a xe2x80x9chandoff backxe2x80x9d, while a handoff from the serving exchange to another exchange (which is not involved in the call path) is referred to as a xe2x80x9chandoff forwardxe2x80x9d.
Such handoffs are typically successful, unless other exchanges are involved. For example, when a handoff forward with path minimization occurs (in which an additional Tandem exchange is involved), the handoff may not be successful due to the additional time required to pass a message (i.e. Handoff to Third or Handoff to Third 2) through the Tandem exchange, because the message transmission requires more time than the default response timer value in the serving exchange allows.
Thus, what is needed is, a system and method providing the ability to dynamically regenerate timers within nodal entities so as to accommodate message passing between such entities along an extended communication path. However, dynamic timer regeneration should not be unlimited, while still providing a reasonable amount of time for each message, as it is passed from one node to another, to secure a response. Therefore, each message transaction should result in the initiation of a new timeout activity and regeneration of any previous timeout activities which are currently pending. Such a system and method should be easily integrated into current standards, such as ANSI 41-D. Also, such a system and method should be easily accommodated by currently available equipment and software.
The present invention solves the foregoing problems arising from messages passed between several nodal entities by providing a method and system for dynamic timer regeneration within each of the nodal entities along the path. In the most basic form, three nodes within a communications network, wherein the first and second nodes comprise a first and second response timer, respectively, can make use of the method during the process of opening a transaction by sending a first message from the first node to the second node, starting the first response timer as prompted by sending the first message, sending a second message from the second node to the third node as prompted by receipt of the first message, starting the second response timer as prompted by sending the second message, sending a message from the second node to the first node to restart the first response timer as prompted by receipt of the first message and sending the second message, sending a first response message from the third node to the second node in response to receipt of the second message, and closing the transaction without unnecessary timeout errors by sending a response message from the second node to the first node in response to receipt of the first response message.
Such a method, wherein the first, second, and third nodes may all comprise MSCs, prevents the occurrence of unnecessary timeout errors by restarting the response timer of each node along a network path as the message is passed from node to node, until it reaches the terminal node in the pathway. Of course, the nodes in the network may comprise any number of nodal entities, such as MSCs, Service Control Functions (SCFs), Intelligent Peripherals (IPs), etc.
A wireless communication signaling network comprising a plurality of nodes engaged in a Transaction Capability Application Part (TCAP) transaction may also be used to support the method of the present invention. In this case, the transaction is a TCAP transaction, and the message sent between the nodes will typically be an Invoke message. The restart message for response timers is typically a TCAP message with a Package Type Identifier of Conversation Without Permission, and a Component Portion including an Invoke (Last) component.
A system comprising a plurality of nodes in a wireless communication signaling network adapted to support a TCAP transaction using dynamic timer regeneration may comprise a first, second, and third node, wherein the first and second nodes each comprise a first and second response timer, respectively. The first node is adapted to receive a third TCAP message to restart the first response timer and a second response message from the second node to stop the countdown activity of the first response timer. The second node is adapted to send a third message (to restart the first response timer) to the first node upon receipt of a first TCAP message from the first node, and to receive a first response message from the third node which stops the countdown activity of the second response timer. The third node is adapted to send a first response message to the second node upon receipt of a second TCAP message from the second node. The third TCAP message is typically an Invoke message.
In each embodiment, dynamic timer regeneration should not be unlimited. A reasonable amount of time should be provided to support the Restart Timer Message timeout period for each message in the forward communications path.